Natural number set includes all natural numbers, namely 0 and all positive integers. Natural numbers are the earliest numbers in human history, which are used to count and indicate the order of things. In mathematics, natural number set is usually represented by the symbol n, sometimes including zero, which is recorded as n? , but does not include any negative numbers. Natural number set is one of the most basic and important data sets in mathematics, which is widely used in mathematics, physics, computer science and other fields.